Author Of 2 Presentations
PS06.03 - The antigenic repertoire of CSF-derived B cells in early untreated multiple sclerosis.
B cell depleting therapies are highly effective treatments for multiple sclerosis (MS). B cells are more numerous in active than inactive lesions, and their intrathecal clonal expansion and oligoclonal band production are hallmarks of MS. B cells also present antigens to T cells and secrete inflammatory cytokines. The antigenic specificity of individual B cells in cerebrospinal fluid (CSF) obtained from patients with early MS may help further clarify the role of B cells in MS biology.
To determine the viral and autoantigen repertoire of CSF-derived, class-switched B cells from untreated, early MS patients.
We performed single cell immunoglobulin sequencing on CSF plasma cells, plasmablasts, and class switched memory B cells from 9 untreated patients: five with relapsing remitting MS (RRMS) and four with clinically isolated syndrome (CIS). The interval between the first attack and lumbar puncture ranged from 1 - 222 days (median 67 days). Brain and spinal cord MRIs performed concurrently with lumbar punctures revealed 5/9 patients with gadolinium enhancing lesions.
Using paired heavy and light chain immunoglobulin sequences, we generated 75 monoclonal antibodies (mAbs) and screened them on a suite of unbiased antigen discovery platforms: 1) mouse brain tissue staining, 2) whole human proteome programmable phage display, 3) pan-viral programmable phage display, 4) mouse and human brain immunoprecipitation mass spectrometry.
The mAbs showed diverse antigen specificities. Candidate antigens were primarily ubiquitously expressed, intracellular proteins; however, a minority were macromolecules associated with the plasma membrane and/or enriched in brain tissue. Shared antigenic targets were occasionally identified within subjects but were rarely identified across subjects, with the latter including cytoskeletal proteins. For two mAbs, high-confidence antigens with prima facie relevance to MS were identified: 1) a white matter-restricted lipid species, and 2) an Epstein-Barr virus-interacting host protein.
Using our panel of 75 mAbs derived from plasma cells, plasmablasts, and class-switched memory B cells found in the CSF of early, untreated RRMS/CIS patients, we identified a diverse repertoire of antigenic targets, with a majority comprised of intracellular host proteins.
SS02.03 - Evidence of an Increased Burden of Humoral Autoimmunity in the CSF and plasma of COVID-19 Patients with Comorbid Neurologic Dysfunction
Coronavirus disease 19 (COVID-19) is the most globally impactful pandemic of the past century. The causative pathogen, SARS-CoV-2, infects ACE2-expressing cells and leads to pulmonary disease and a systemic immune response. In patients with severe COVID-19, a dysregulated immune response is associated with secondary extrapulmonary dysfunction, including neurological symptoms. Neurologic complications of SARS-CoV-2 infection are increasingly recognized, yet it is unknown to what degree humoral autoimmunity is a feature of neurological impairment in COVID-19.
To perform an unbiased survey of peripheral and central humoral autoimmunity in COVID-19 patients with neurologic dysfunction.
Paired cerebrospinal fluid (CSF) and plasma biospecimens were collected from nasopharyngeal (NP) SARS-CoV-2 PCR positive patients with comorbid neurologic impairment (n = 5). Additional unpaired CSF biospecimens were collected from neurologically impaired NP PCR positive patients (n = 3). All COVID-19 patients were PCR negative for SARS-CoV-2 in the CSF. CSF and plasma were also collected from SARS-CoV-2 uninfected healthy control volunteers. Neurologic syndromes were diverse and included myositis, seizures, and encephalopathy. Biospecimens were screened in replicate by mouse brain immunostaining, immunoprecipitation mass spectrometry (IP-MS), and human peptidome phage display immunoprecipitation sequencing (PhIP-Seq). IP-MS spectra were analyzed by both spectral counting and MS1 peak area. For PhIP-Seq, proteins with overlapping peptides that were enriched at least 10-fold above control samples, or single peptides enriched 100-fold above controls were considered candidate autoantigens. Candidate autoantigens identified by at least two of three methods (PhIP-Seq, spectral counting, and peak area) were carried forward for validation.
Unexpectedly, seven of eight COVID-19 CSF samples had evidence of humoral autoimmunity by tissue staining (n = 7), and IP-MS (n = 6), PhIP-Seq (n = 7), or both (n = 6). By IP-MS, significantly more candidate autoantigens were identified in COVID-19 biospecimens than in uninfected controls. PhIP-Seq identified twice as many candidate autoantigens in COVID-19 biospecimens than in controls. Notably, COVID-19 biospecimens were enriched for clinically relevant candidate autoantigens including those associated with dermatomyositis, and myasthenia gravis (none known to be pre-existing comorbidities). Additionally, COVID-19 biospecimens were enriched for candidate autoantigens with prima facie clinical relevance as they targeted proteins enriched in skeletal muscle, endothelial cells, and at the synapse. One candidate autoantibody targeted a ciliary protein implicated in syndromic anosmia.
We identified evidence of an increased burden of humoral autoimmunity in COVID-19 patients with comorbid neurologic dysfunction.